<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .main {
            width: 30px;
            height: 30px;
            border-width: 20px 20px 20px 20px;
            border-style: solid;
            border-color: red blue green yellow;
        }

        .three {
            width: 0;
            border-width: 20px 0px 20px 20px;
            border-style: solid;
            border-color: transparent transparent currentColor transparent;
        }
    </style>
</head>

<body>

    <body>
        <div class="main"></div>
        <div class="three"></div>
    </body>
</body>

</html>